The present invention relates to a construction machine control system when a construction machine is operated for construction work using a rotary laser irradiating system for forming a reference plane for construction work such as ground leveling operation, and in particular, to a construction machine control system using a laser reference plane formed by rotary irradiation of laser beam for the control of height for ground leveling.
When ground leveling operation for preparing a projected housing area or for paving roads is performed using construction machines such as graders, bulldozers, etc., it is necessary to have a reference for detecting position of the construction machines or for determining height of ground leveling. In recent years, a construction machine control system has been introduced for practical use, which measures and detects ground leveling position of the construction machine by GPS (global positioning system) and uses laser beams to determine height as a reference for ground leveling operation. To form a reference plane for height as described above, a construction machine control system using a rotary laser irradiating system is employed.
FIG. 15 shows a case where this construction machine control system is adopted for a bulldozer.
In FIG. 15, reference numeral 1 represents a rotary laser irradiating system, and 2 represents a bulldozer. The rotary laser irradiating system 1 is installed via a tripod 3 at a predetermined position of a projected housing area. The rotary laser irradiating system 1 projects laser beam 4 in a horizontal direction and rotates the beams, and a reference plane is formed by the laser beam 4.
The bulldozer 2 is equipped with a blade 5, which is supported in such manner that it can be moved up or down. A pole 6 is erected on the blade 5, and a level sensor 7 is mounted on the pole 6. The level sensor 7 receives the laser beam 4 from the rotary laser irradiating system 1 and detects photodetecting position. The bulldozer 2 is provided with a control device (not shown), which detects position of the height of the blade 5 based on a photodetection signal from the level sensor 7 and controls height of the blade 5 according to the result of the detection.
As described above, a horizontal reference plane is formed by the laser beam 4, and ground can be leveled in the horizontal direction by keeping a constant distance between the horizontal reference plane and a blade edge 5' of the blade 5. Also, it is possible to change height of the ground surface to be leveled by changing the distance to the blade edge 5'.
Rough description is now given on a GPS system for measuring position of the bulldozer 2 referring to FIG. 16.
A GPS base antenna 8 is installed at a known position, and a GPS antenna 9 is erected on the bulldozer 2. The GPS base antenna 8 and the GPS antenna 9 receive signals from an artificial satellite 10 respectively and detect positions. By comparing the two positions thus detected, working position of the bulldozer 2 with respect to the GPS base antenna 8 at the known point is calculated, and ground leveling operation is performed for a predetermined range.
At a construction site of relatively smaller scale, only one construction machine is used, while a plurality of construction machines are generally used at the same time at construction site. Further, when a plurality of construction machines are used for construction work, height of ground leveling also may differ for each construction machine. Therefore, there is a problem in that a rotary laser irradiating system is required for level setting for each of the plurality of construction machines. When a plurality of rotary laser irradiating systems are operated, the construction machine on the receiving side may recognize a plurality of laser beam reference planes, and this often leads to erroneous operation.
To ensure simultaneous control of a plurality of construction machines without causing erroneous operation, it is preferable to perform level setting using a single rotary laser irradiating system. In order to perform level setting using a single rotary laser irradiating system for each of construction machines, it is necessary to perform level setting for each of the construction machines during one rotation of the laser beam. Conventionally, laser beam is irradiated by rotary irradiation from an optical head, which is rotated at several hundreds of rpm to set a reference plane or a reference line. Also, for the setting of level and inclination, tilting mechanism for tilting the optical head is provided.
However, in the tilting mechanism as described above, it is impossible to adjust at high speed in a vertical direction such as level setting in a plurality of directions during one rotation of the laser beam. In this respect, a construction machine control system is not yet used in practical application, which uses a single rotary laser irradiating system to control ground leveling operation for a plurality of construction machines.
Further, ground leveling operation is not always limited to the preparation of horizontal ground surface. Rather, leveling operation must be performed for preparation of inclined surface in many cases. In the construction work for preparing a projected housing area, it is necessary to provide gradient for water drainage. For road paving work, gradient suitable for topographical condition and gradient for water drainage must be provided. In a conventional type construction machine control system, a horizontal ground surface is prepared at first, and an inclined ground surface is then prepared with a predetermined gradient according to the result of survey operation.
The horizontal ground surface can be prepared by the construction machine control system as described above without requiring skill of the operator, while it is very difficult and requires skilled operator to provide gradient to the ground surface. Finishing condition of the ground leveling of inclined ground surface depends much on the skilled technique of operator. Progress of the work also depends on the skill of the operator, and this involves the problem of completion time and process control. There is also a case where horizontal ground surfaces with different levels must be prepared at the same construction site. In such case, complicated procedure is required and level setting for a reference plane formed by rotary laser irradiation must be repeatedly performed.